This invention relates to vehicle emissions control, and particularly to a refueling vapor recovery system designed to capture, store, and subsequently purge the fuel vapors that are displaced and generated during a typical vehicle refueling operation.
Polluting emissions are released into the atmosphere during each and every motor vehicle refueling activity. Typically, removal of a fuel cap permits pressurized fuel vapors present within the vehicle fuel system to escape to the atmosphere. In view of the frequency of vehicle refueling activities, it will be appreciated that a significant quantity of otherwise combustible fuel is lost to the atmosphere each time a vehicle is refueled.
New fuel vapors are generated during refueling due to splash and agitation of the dispensed fuel, as well as from potential temperature differences between the fuel tank and the dispensed fuel. In addition, as the liquid fuel dispensed at the pump fills the vehicle fuel tank, fuel vapors that are present in the tank and generated during refueling are displaced by liquid fuel. These displaced fuel vapors are moved out of the fuel tank vapor space by the displacing action of the liquid fuel. In conventional vehicle fuel systems, these displaced vapors are released directly into the atmosphere via the fuel tank filler neck and are a contributing factor to air pollution.
One object of the present invention is to provide an emissions control system for advantageously capturing fuel vapors normally discharged during a vehicle refueling activity so as to reduce waste of fuel energy resources, assist in reducing the level of air pollution, and avoid the shortcomings of conventional vehicle fuel systems.
Another object of the present invention is to provide a fuel vapor recovery system that conforms to all government environmental and safety regulations regarding evaporative and refueling emissions, exhaust emissions, and vehicle impact, and that also satisfies customer-perceived vehicle functions such as drivability, ease of refueling, and control of fuel vapor odor.
According to the present invention, a vapor control system includes partition means for sealing a fuel dispensing nozzle to a fuel tank filler neck during refueling to prevent loss of fuel vapor to the atmosphere and separator means for separating liquid fuel entrained in the fuel vapor from fuel vapor discharged from the fuel tank via a fill-limiting vent tube. Preferably, the partition means divides the fuel tank filler neck into separate sealed inner and outer chambers and is configured to admit a fuel-dispensing nozzle into the inner chamber without coupling the inner and outer chambers together in fluid communication during refueling. Vapor recovery means is provided for selectively processing fuel vapor discharged from the separator means to reduce environmentally hazardous emissions without discharging unprocessed fuel vapor to the atmosphere during refueling.
In preferred embodiments, the vapor recovery means selectively delivers fuel vapor discharged from the separator means to a carbon canister or other vapor condenser positioned elsewhere in the vehicle, thereby reducing the mass of fuel discharged into the atmosphere during refueling. The vapor recovery means includes actuation means in a vapor flow passage for automatically moving a refueling control valve, which valve is normally spring-biased to its passage-closing position, to its passage-opening position. This permits fuel vapor discharged from the fuel tank during each refueling activity to be conducted to the canister for liquid fuel recovery treatment therein prior to being discharged to the atmosphere. Preferably, the actuation means includes means for sensing the beginning of a vehicle refueling activity cycle.
A fuel cap is provided for closing and sealing the mouth of the fuel tank filler neck. In preferred embodiments, sufficient loosening of the fuel cap on the filler neck actuates the refueling control valve to initiate a vapor recovery sequence without breaking the vapor seal provided by the fuel cap or otherwise permitting untreated fuel vapor to be discharged directly into the atmosphere. The sensing means includes a control pad movable relative to the filler neck between positions in close proximity to the mouth of the filler neck. Illustratively, the control pad is spring-biased against the fuel cap whenever the fuel cap is mounted on the filler neck. Illustratively, a mechanical linkage is provided for moving the refueling control valve to its passage-opening position in response to spring-biased movement of the control pad during removal of the fuel cap. In this way, fuel vapor discharged from the fuel tank is conducted automatically to a fuel vapor treatment site such as a canister instead of being discharged directly into the atmosphere through the filler neck mouth.
Also in preferred embodiments, the vapor control system further includes a safety pressure-relief valve for exhausting fuel vapor discharged from the separator means directly to the atmosphere during disablement of the vapor recovery means. Any pressurized fuel vapor in excess of design limits is vented to the outer chamber for discharge to the atmosphere whenever vapor flow exceeds the capacity of the system. Preferably, the pressure-relief valve is a "whistle" valve. In other words, this valve is configured to issue a sonic warning to a refueling attendant whenever the pressure-relief valve is activated so that necessary corrective action can be taken to repair flow blockage in the system.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.